The invention relates to assembly of a catalytic converter having a catalyst substrate surrounded by a support mat housed within an outer shell. More specifically, the invention pertains to post calibration converter canning enabling confirmed integrity of gap bulk density throughout the life of the converter.
One known type of catalytic converter for automotive exhaust applications is shown in FIG. 6. Catalytic converter 1 comprises an open ended, tubular sheet metal body 3, the inside of which defines a chamber 5 for a ceramic monolith, honeycomb-type, catalyst substrate 7 having flat ends 9 and a great number of catalyst coated, longitudinal honeycombed cell passages 11 extending from one end to the other. The central portion of the substrate 7 is surrounded by an annular, shock absorbent, resilient, insulative support mat 13, which is preferably fashioned from a gas impervious vermiculite based material that expands substantially upon heating. Mat 13 is compressed at assembly to about one half of its initial thickness. The opposite end portions 15 of the body 3 are preferably each formed or swaged to a partially spherical shape as illustrated having central openings substantially less in diameter than the diameter of substrate 7. Gas flow end bushings 17 and 19 have tubular outer ends 21 and 23, respectively, for attachment by welding or clamping or otherwise to the exhaust system conduits (not shown). Bushings 17 and 19 also have outwardly flared annular partially spherical inner end flanges 25 and 27, respectively, each of which is preferably formed on a radius corresponding to that of the body end portions 15 to which they are welded in selected locations so that their ends 21 and 23 have the desired orientation with respect to the center line or axis of body 3.
Known assembly methods using pre-calibration have potential for shear damage to the support mat and/or the converter substrate during stuffing into the outer shell of the converter. Hence, there is a need for a process and arrangement for stuffing a mat/substrate sub-assembly into a converter shell and then to size the converter can to a predetermined diameter to achieve a desired gap bulk density of the support mat without the stuffing damage incurred with prior art approaches.